A prior art semiconductor wafer fragment 10 is illustrated in FIG. 1. Wafer fragment 10 comprises a substrate 12 and conductive electrical components 14, 16 and 18 overlying substrate 12. Conductive electrical components 14, 16 and 18 may comprise, for example, conductive lines. Such conductive lines may be formed from metal, or conductively-doped polysilicon. Between conductive components 14, 16 and 18 is formed an insulative material 20. Material 20 electrically isolates conductive elements 14, 16 and 18 from one another. Insulative material 20 may comprise materials known to persons of ordinary skill in the art, including, for example, silicon dioxide, silicon nitride, and undoped silicon. Although each of these materials has good insulative properties, the materials disadvantageously have high dielectric constants which can lead to capacitive coupling between proximate conductive elements, such as elements 14, 16 and 18. For instance, silicon nitride has a dielectric constant of about 8 and undoped silicon has a dielectric constant of about 11.8.
A prior art method for insulating conductive elements 14, 16 and 18 from one another, while reducing a dielectric constant of a material between conductive elements 14, 16 and 18 is illustrated in FIGS. 2 and 3. In referring to FIGS. 2 and 3, similar numbers to those utilized in FIG. 1 will be used, with differences indicated by the suffix "a" or by different numerals.
Referring to FIG. 2, a semiconductor wafer fragment 10a is illustrated. Fragment 10a comprises a substrate 12a, and overlying conductive lines 14a, 16a and 18a. Between lines 14a, 16a and 18a is a carbon layer 22. Conductive lines 14a, 16a and 18a are inlaid within carbon layer 22 by a damascene method. A thin, gas-permeable, silicon dioxide layer 24 is formed over conductive lines 14a, 16a and 18a, and over carbon layer 22.
Referring to FIG. 3, carbon layer 22 is vaporized to form voids 26 between conductive elements 14a, 16a and 18a. Voids 26 contain a gas. Gasses advantageously have dielectric constants of about 1.
It would be desirable to develop alternative methods for insulating conductive elements from one another with low-dielectric-constant materials.